Image sensing apparatus

ABSTRACT

There is disclosed an apparatus having an image sensing device, a signal processing device for performing a first image sensing operation for making the image sensing device perform an image sensing operation in an exposure state to obtain a sensed image signal, and a second image sensing operation for making the image sensing device perform an image sensing operation in a non-exposure state to obtain a sensed image signal, and processing the sensed image signal obtained by the first image sensing operation by the sensed image signal obtained by the second image sensing operation, the signal processing device having a first mode for making the image sensing device perform the first image sensing operation and then the second image sensing operation, and a second mode for making the image sensing device perform the second image sensing operation and then the first image sensing operation, and a storage device for storing signals obtained in the first and second modes processed by the signal processing device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image sensing apparatus for sensing a still image and/or moving image.

2. Description of the Related Art

Conventionally, image sensing apparatuses such as electronic cameras and the like, which record/play back still images and moving images sensed by a solid-state image sensing element such as a CCD or the like using memory cards having solid-state memory elements as recording media, have already been commercially available.

In such electronic camera, a single shot mode for sensing images frame by frame every time the shutter button is pressed, and a continuous shot mode for sensing images successively while the shutter button is held down can be switched by selecting either mode.

On the other hand, when an image is sensed using a solid-state image sensing element such as a CCD or the like, a dark noise correction process can be done by computations using dark image data which is read out after charge accumulation in the same manner as in actual image sensing while the image sensing element is not exposed, and actually sensed image data which is read out after charge accumulation while the image sensing element is exposed.

With this process, sensed image data can be corrected in terms of image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element and small scratches unique to the image sensing element, thus obtaining a high-quality sensed image.

Especially, since dark current noise increases with increasing charge accumulation time and temperature rise of the image sensing element, if exposure for a long period of time (seconds) or at high temperature is done, a great image quality improvement effect can be obtained, and the dark noise correction process is a function effective for the electronic camera users.

However, in the conventional image sensing apparatus such as an electronic camera or the like, when actual image sensing is done after dark image data is sensed, the shutter release time lag becomes longer by the dark image sensing time in the single shot mode, thus missing a shutter chance.

On the other hand, when dark image data is sensed after actual image sensing, the image sensing interval between the first and second frames is prolonged by the dark image sensing time in the continuous shot mode. As a result, constant image sensing frame intervals cannot be set.

SUMMARY OF THE INVENTION

One aspect of the present invention is to provide an apparatus, which comprises an image sensing device, a signal processing device for performing a first image sensing operation for making the image sensing device perform an image sensing operation in an exposure state to obtain a sensed image signal, and a second image sensing operation for making the image sensing device perform an image sensing operation in a non-exposure state to obtain a sensed image signal, and processing the sensed image signal obtained by the first image sensing operation by the sensed image signal obtained by the second image sensing operation, the signal processing device having a first mode for making the image sensing device perform the first image sensing operation and then the second image sensing operation, and a second mode for making the image sensing device perform the second image sensing operation and then the first image sensing operation, and a storage device for storing signals obtained in the first and second modes processed by the signal processing device, thereby preventing a shutter chance from being missed, and setting constant image sensing frame intervals.

Another aspect of the present invention is to provide an apparatus, which comprises an image sensing device, a signal processing device for performing a first image sensing operation for making the image sensing device perform an image sensing operation in an exposure state to obtain a sensed image signal, and a second image sensing operation for making the image sensing device perform an image sensing operation in a non-exposure state to obtain a sensed image signal, and processing the sensed image signal obtained by the first image sensing operation by the sensed image signal obtained by the second image sensing operation, the signal processing device having a first mode for making the image sensing device perform the first image sensing operation and then the second image sensing operation, and a second mode for making the image sensing device perform the second image sensing operation and then the first image sensing operation, and a switching device for switching the signal processing device between the first and second modes in accordance with a state of shutter release operation, thereby preventing a shutter chance from being missed, and setting constant image sensing frame intervals.

Another aspect of the present invention is to provide an apparatus, which comprises an image sensing device, a signal processing device for performing a first image sensing operation for making the image sensing device perform an image sensing operation in an exposure state to obtain a sensed image signal, and a second image sensing operation for making the image sensing device perform an image sensing operation in a non-exposure state to obtain a sensed image signal, and processing the sensed image signal obtained by the first image sensing operation by the sensed image signal obtained by the second image sensing operation, the signal processing device having a first mode for making the image sensing device perform the first image sensing operation and then the second image sensing operation, and a second mode for making the image sensing device perform the second image sensing operation and then the first image sensing operation, and a switching device for switching the signal processing device to the first mode when the exposure start instruction device issues an exposure start instruction while the signal processing device is executing the second image sensing operation in the second mode, thereby preventing a shutter chance from being missed, and setting constant image sensing frame intervals.

Another aspect of the present invention is to provide an apparatus, which comprises an image sensing device, an exposure instruction device for issuing an exposure preparation instruction at a first stroke position of a shutter release member, and issuing an exposure start instruction at a second stroke position of the shutter release member, and a signal processing device for performing a first image sensing operation for making the image sensing device perform an image sensing operation in an exposure state to obtain a sensed image signal, and a second image sensing operation for making the image sensing device perform an image sensing operation in a non-exposure state to obtain a sensed image signal, and processing the sensed image signal obtained by the first image sensing operation by the sensed image signal obtained by the second image sensing operation, the signal processing device performing the second image sensing operation in response to the exposure preparation instruction issued by the exposure instruction device, and performing the first image sensing operation in response to the exposure start instruction issued by the exposure instruction device, thereby preventing a shutter chance from being missed, and setting constant image sensing frame intervals.

Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the arrangement of an image sensing apparatus according to the first embodiment of the present invention;

FIG. 2 is a flow chart of a main routine showing the control sequence of the image sensing apparatus;

FIG. 3 is a flow chart of the main routine showing the control sequence of the image sensing apparatus and continued from FIG. 2;

FIG. 4 is a flow chart of the main routine showing the control sequence of the image sensing apparatus and continued from FIG. 3;

FIG. 5 is a flow chart showing the sequence of a distance measurement/photometry process in step S132 in FIG. 3 in detail;

FIG. 6 is a flow chart showing the sequence of an image sensing process in step S163 in FIG. 4 in detail;

FIG. 7 is a flow chart showing the sequence of a dark capture (1) process in step S137 in FIG. 3 in detail;

FIG. 8 is a flow chart showing the sequence of a dark capture (2) process in step S166 in FIG. 4 in detail;

FIG. 9 is a timing chart showing the flow of image sensing operation in the first embodiment;

FIG. 10 is a flow chart of a main routine showing the control sequence of an image sensing apparatus according to the second embodiment;

FIG. 11 is a flow chart of the main routine showing the control sequence of the image sensing apparatus according to the second embodiment and continued from FIG. 10;

FIG. 12 is a flow chart of the main routine showing the control sequence of the image sensing apparatus according to the second embodiment and continued from FIG. 11; and

FIG. 13 is a timing chart showing the flow of image sensing operation in the second embodiment

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a block diagram showing the arrangement of an image sensing apparatus according to the first embodiment of the present invention.

Referring to FIG. 1, reference numeral 100 denotes an image sensing apparatus.

Reference numeral 12 denotes a shutter for controlling the exposure amount on an image sensing element; and 14, an image sensing element such as a CCD, CMOS, or the like for converting an optical image into an electrical signal.

Light rays that have entered a lens 310 are guided onto the image sensing element 14 via a stop 312, lens mounts 306 and 106, a mirror 130, and the shutter 12 by a single-lens reflex system, and form an optical image on the image sensing element 14.

Reference numeral 16 denotes an A/D converter for converting an analog signal output into a digital signal.

Reference numeral 18 denotes a timing generation circuit for supplying clock signals and control signals to the image sensing element 14, the A/D converter 16, and a D/A converter 26. The timing generation circuit 18 is controlled by a memory control circuit 22 and system control circuit 50.

Reference numeral 20 denotes an image processing circuit for performing a predetermined pixel interpolation process and color conversion process for data from the A/D converter 16 or the memory control circuit 22.

Also, the image processing circuit 20 can execute a TTL (through the lens) AF (auto-focus) process, AE (auto-exposure) process, and EF (flash light control) process. In these processes, the image processing circuit 20 makes predetermined computations using sensed image data as needed, and the system control circuit 50 controls a shutter control circuit 40 and distance measurement circuit 42 on the basis of the obtained computation result.

Furthermore, the image processing circuit 20 makes predetermined computations using sensed image data, and executes a TTL AWB (auto white balance) process on the basis of the obtained computation result.

Since this embodiment comprises the distance measurement circuit 42 and a photometry circuit 46 dedicated to those processes, the AF, AE, and EF processes may be done using the distance measurement circuit 42 and photometry circuit 46 in place of those using the image processing circuit 20.

Alternatively, the AF, AE, and EF processes may be done using the distance measurement circuit 42 and photometry circuit 46 in addition to those using the image processing circuit 20.

Reference numeral 22 denotes a memory control circuit which controls the A/D converter 16, the timing generation circuit 18, the image processing circuit 20, an image display memory 24, the D/A converter 26, a memory 30, and a compression/expansion circuit 32.

Data output from the A/D converter 16 is written in the image display memory 24 or memory 30 via the image processing circuit 20 and memory control circuit 22 or via the memory control circuit 22 alone.

Reference numeral 24 denotes an image display memory; 26, a D/A converter; and 28, an image display unit comprising, e.g., a TFT LCT or the like. Display image data written in the image display memory 24 is displayed on the image display unit 28 via the D/A converter 26.

When sensed image data is displayed using the image display unit 28 as needed, an electronic viewfinder function can be implemented.

The image display unit 28 can turn on/off its display in accordance with an instruction from the system control circuit 50. When the display is OFF, great power savings of the image sensing apparatus 100 can be achieved.

Reference numeral 30 denotes a memory for storing sensed still or moving images. The memory 30 has a sufficient memory size capable of storing a predetermined number of still images or a moving image for a predetermined period of time. Hence, even in a continuous shot mode or panorama mode for continuously sensing a plurality of still images, a large number of images can be written in the memory 30 at high speed.

Also, the memory 30 can be used as a work area of the system control circuit 50.

Reference numeral 32 denotes a compression/expansion circuit for compressing/expanding image data by the adaptive discrete cosine transform (ADCT), wavelet transform, or the like. The compression/expansion circuit 32 loads an image stored in the memory 30, compresses or expands it, and writes the compressed or expanded data in the memory 30.

Reference numeral 40 denotes a shutter control circuit for controlling the shutter 12 on the basis of photometry information from the photometry circuit 46 in cooperation with a stop control circuit 340 that controls the stop 312.

Reference numeral 42 denotes a distance measurement circuit used to execute the AF process. Light rays that have entered the lens 310 are guided to the distance measurement circuit 42 via the stop 312, the lens mounts 306 and 106, the mirror 130, and a distance measurement sub-mirror (not shown) by the single-lens reflex system, thus measuring the focusing state of an image formed as an optical image.

Reference numeral 46 denotes a photometry circuit used to execute the AE process. Light rays that have entered the lens 310 are guided to the photometry circuit 46 via the stop 312, the lens mounts 306 and 106, the mirror 130 and a mirror 132, and a photometry lens (not shown), thus measuring the exposure state of an image formed as an optical image.

The photometry circuit 46 also has an EF process function in cooperation with an electronic flash 48.

Reference numeral 48 denotes an electronic flash which has a function of projecting AF assist light, and a flash light control function.

Note that the system control circuit 50 can perform exposure control and AF control using a video TTL scheme for the shutter control circuit 40, stop control circuit 340, and distance measurement control circuit 342 on the basis of a computation result of image data output from the image sensing element 14 by the image processing circuit 20.

Furthermore, AF control may be done using both the measurement result of the distance measurement circuit 42 and the computation result of image data output from the image sensing element 14 by the image processing circuit 20.

Moreover, exposure control may be done using both the measurement result of the photometry circuit 46 and the computation result of image data output from the image sensing element 14 by the image processing circuit 20.

Reference numeral 50 denotes a system control circuit for controlling the overall image sensing apparatus 100; and 52, a memory for storing constants, variables, programs, and the like required for operating the system control circuit 50.

Reference numeral 54 denotes an indication unit which comprises a liquid crystal display device, loudspeaker, and the like, and indicates the operation state, messages, and the like using characters, images, sound, and the like in accordance with execution of programs in the system control circuit 50. The indication unit 54 is set at one or a plurality of easy-to-see positions around the console of the image sensing apparatus 100, and is constructed by a combination of an LCD, LEDs, sound generation element, and the like. Some functions of the indication unit 54 are set within an optical viewfinder 104.

Of the indication contents of the indication unit 54, those displayed on the LCD or the like include, e.g., a single/continuous shot indication, self timer indication, compression ratio indication, recording pixel count indicating, recorded image count indication, remaining recordable image count indication, shutter speed indication, aperture value indication, exposure correction indication, flash indication, red-eye suppression indication, macro image sensing indication, buzzer setup indication, remaining timepiece battery capacity indication, remaining battery capacity indication, error indication, information indication using numerals of a plurality of digits, attachment/detachment indication of recording media 200 and 210, attachment/detachment indication of a lens unit 300, communication I/F operation indication, date/time indication, connection indication with an external computer, and the like.

Of the indication contents of the indication unit 54, those displayed within the optical viewfinder 104 include, e.g., in-focus indication, image sensing ready indication, camera shake alert indication, flash charging indication, flash charging completion indication, shutter speed indication, aperture value indication, exposure correction indication, recording medium write access indication, and the like.

Furthermore, of the indication contents of the indication unit 54, those displayed using the LEDs and the like include, e.g., in-focus indication, image sensing ready indication, camera shake alert indication, flash charging indication, flash charging completion indication, recording medium write access indication, macro image sensing setup notification, secondary battery charging state indication, and the like.

Of the indication contents of the indication unit 54, those indicated by lamps and the like include, e.g., a self timer notification lamp, and the like. The self timer notification lamp may be commonly used as AF assist light.

Reference numeral 56 denotes an electrically erasable/programmable nonvolatile memory, which uses, e.g., an EEPROM or the like.

Reference numerals 60, 62, 64, 66, 68, and 70 denote operation units for inputting various operation instructions of a system control circuit 118. These operation units are constructed by one or a plurality of combinations of a switch, a dial, a touch panel, a pointer using line of sight detection, a voice recognition device, and the like.

Examples of these operation units will be explained below.

Reference numeral 60 denotes a mode dial switch which can selectively set one of various function image sensing modes: an automatic image sensing mode, programmed image sensing mode, shutter speed priority image sensing mode, aperture priority image sensing mode, manual image sensing mode, focal depth priority (depth) image sensing mode, portrait image sensing mode, landscape image sensing mode, macro image sensing mode, sport image sensing mode, night scene image sensing mode, panorama image sensing mode, and the like.

Reference numeral 62 denotes a shutter switch SW1, which is turned on at the middle (half stroke position) of operation of a shutter button (not shown), and instructs start of the AF process, AE process, AWB process, EF process, and the like.

Reference numeral 64 denotes a shutter switch SW2, which is turned on upon completion of operation (at the full stroke position) of the shutter button (not shown), and instructs start of a series of processes including an exposure process for writing a signal read out from the image sensing element 14 as image data in the memory 30 via the A/D converter 16 and memory control circuit 22, a development process using computation results in the image processing circuit 20 and memory control circuit 22, and a recording process for reading out image data from the memory 30, compressing the readout data by the compression/expansion circuit 32, and writing the compressed image data in the recording medium 200 or 210.

Reference numeral 66 denotes a playback switch which instructs to start playback operation for reading out an image sensed in a given image sensing mode from one of the memory 30 and the recording media 200 and 210, and displaying the readout image on the image display unit 28.

Reference numeral 68 denotes a single/continuous shot switch, which can set one of a single shot mode for sensing one frame of image upon depression of the shutter switch SW2, and then setting a standby state, and a continuous shot mode for successively sensing images while the shutter switch SW2 is held down.

Reference numeral 70 denotes a console including various buttons, touch panel, and the like, which include a menu button, set button, macro button, multi-frame playback new page button, flash setup button, single shot/continuous shot/self timer switch button, menu move+(plus) button, menu move−(minus) button, playback image move+(plus) button, playback image move−(minus) button, sensed image quality select button, exposure correct button, date/time setup button, select/change button that can select and change various functions upon executing image sensing and playback in, e.g., the panoramic mode, determine/execute button which can determine and execute various functions upon executing image sensing and playback in, e.g., the panoramic mode, image display ON/OFF switch for turning on/off the image display unit 28, quick review ON/OFF setup switch for setting a quick review function of automatically playing back sensed image data immediately after image sensing, compression mode switch for selecting a compression ratio of JPEG compression, and selecting a CCDRAW mode for converting directly converting a signal output from the image sensing element into digital data, and recording the digital data in a recording medium, playback mode switch for setting various function modes such as a playback mode, multi-frame playback/delete mode, PC connect mode, and the like, AF mode setup switch which can set a one-shot AE mode for starting auto-focusing upon depression of the shutter switch SW1, and maintaining an in-focus state once it is attained, and a servo AF mode for continuously executing auto-focusing while the shutter switch SW1 is held down, and the like.

In place of the plus and minus buttons, a rotary dial switch may be used to select numerical values and functions more smoothly.

Reference numeral 72 denotes a power switch which can selectively set power-ON and power-OFF modes of the image sensing apparatus 100. Also, the power switch 72 can also selectively set power-ON and power-OFF modes of various accessories such as the lens unit 300, external electronic flash, recording media 200 and 210, and the like, which are connected to the image sensing apparatus 100.

Reference numeral 80 denotes a power supply control circuit which is comprised of a battery detection circuit, a DC-DC converter, a switch circuit for switching a block to be energized, and the like. The power supply control circuit 80 detects the presence/absence, type, and remaining battery amount of a battery attached, controls the DC-DC converter on the basis of such detection results and an instruction from the system control circuit 50, and supplies a required voltage to the respective units including the recording media for a required period of time.

Reference numerals 82 and 84 denote connectors; and 86, a power supply circuit. The power supply circuit 86 includes a primary battery such as an alkali battery, lithium battery, or the like, a secondary battery such as an NiCd battery, NiMH battery, Li battery, or the like, an AC adapter, and the like.

Reference numerals 90 and 94 denote interfaces with recording media such as a memory card, hard disk, and the like; 92 and 96, connectors for connecting recording media such as a memory card, hard disk, and the like; and 98, a recording medium attachment/detachment detection circuit for detecting whether or not the recording medium 200 or 210 is attached to the connector 92 and/or the connector 96.

Note that this embodiment has two sets of interfaces and connectors that receive the recording media. However, the number of sets of interfaces and connectors that receive the recording media is not particularly limited. Also, combinations of interfaces and connectors of different standards may be used.

As the interface and connector, those complying with the standards of a PCMCIA card, CF (compact flash) card, and the like may be used.

Furthermore, when the interfaces 90 and 94, and connectors 92 and 96 use those complying with the standards of a PCMCIA card, CF (compact flash) card, and the like, and various communication cards such as a LAN card, modem card, USB card, IEEE1394 card, P1284 card, SCSI card, PHS, and the like are connected thereto, image data and associated management information can be transferred between the image sensing apparatus and an external computer or its peripheral devices such as a printer and the like.

Reference numeral 104 denotes an optical viewfinder which can guide light rays that have entered the lens 310 via the stop 312, lens mounts 306 and 106, mirrors 130 and 132 by the single-lens reflex system, and can form and display them as an optical image. In this manner, without using the electronic viewfinder function implemented by the image display unit 28, image sensing can be done using the optical viewfinder 104 alone. In the optical viewfinder 104, some functions of the indication unit 54, e.g., an in-focus indication, camera shake alert indication, flash charging indication, shutter speed indication, aperture value indication, exposure correction indication, and the like are provided.

Reference numeral 110 denotes a communication circuit having various communication functions such as RS232C, USB, IEEE1394, P1284, SCSI, modem, LAN, radio communication, and the like.

Reference numeral 112 denotes a connector or antenna, which serves as a connector when the image sensing apparatus 100 is connected to another device using the communication means 139, or serves as an antenna in case of radio communications.

Reference numeral 120 denotes an interface for connecting the image sensing apparatus 100 to the lens unit 300 in the lens mount 106; 122, a connector for electrically connecting the image sensing apparatus 100 to the lens unit 300; and 124, a lens attachment/detachment detection circuit for detecting whether or not the lens unit 300 is attached to the lens mount 106 and/or the connector 122.

The connector 122 also has a function of exchanging control signals, status signals, data signals, and the like between the image sensing apparatus 100 and lens unit 300, and supplying currents of various voltages. The connector 122 may communicate not only electrical signals but also optical signals, audio signals, and the like.

Reference numerals 130 and 132 denote mirrors which can guide light rays that have entered the lens 310 to the optical viewfinder 104 by the single-lens reflex system. Note that the mirror 132 may be either a quick return mirror or half mirror.

Reference numeral 200 denotes a recording medium such as a memory card, hard disk, or the like. The recording medium 200 comprises a recording unit 202 comprised of a semiconductor memory, magnetic disk, or the like, an interface 204 with the image sensing apparatus 100, and a connector 206 for connecting the image sensing apparatus 100.

Reference numeral 210 denotes a recording medium such as a memory card, hard disk, or the like. The recording medium 210 comprises a recording unit 212 comprised of a semiconductor memory, magnetic disk, or the like, an interface 214 with the image sensing apparatus 100, and a connector 216 for connecting the image sensing apparatus 100.

Reference numeral 300 denotes an exchangeable lens type lens unit.

Reference numeral 306 denotes a lens mount for mechanically coupling the lens unit 300 to the image sensing apparatus 100. The lens mount 306 includes various functions of electrically connecting the lens unit 300 and image sensing apparatus 100.

Reference numeral 310 denotes a photographing lens; and 312, a stop.

Reference numeral 320 denotes an interface for connecting the lens unit 300 to the image sensing apparatus 100 in the lens mount 306; and 322, a connector for electrically connecting the lens unit 300 to the image sensing apparatus 100. The connector 322 also has a function of exchanging control signals, status signals, data signals, and the like between the image sensing apparatus 100 and lens unit 300, and receiving or supplying currents of various voltages. Note that the connector 322 may communicate not only electrical signals but also optical signals, audio signals, and the like.

Reference numeral 340 denotes a stop control circuit for controlling the stop 312 on the basis of photometry information from the photometry circuit 46 in cooperation with the shutter control circuit 40 that controls the shutter 12.

Reference numeral 342 denotes a distance measurement control circuit for controlling focusing of the photographing lens 310; and 344, a zoom control circuit for controlling zooming of the photographing lens 310.

Reference numeral 350 denotes a lens system control circuit for controlling the overall lens unit 300. The lens system control circuit 350 has a memory function of storing constants, variables, programs, and the like required for operating the lens unit 300, and a nonvolatile memory function of holding identification information such as a number or the like unique to the lens unit 300, management information, function information such as a full-aperture value, minimum aperture value, focal length, and the like, current and past setup values, and the like.

The operation of the image sensing apparatus with the above arrangement will be explained below with reference to FIGS. 2 to 8.

FIGS. 2 to 4 are flow charts of the main routine showing the control sequence of the image sensing apparatus 100. Note that these flow charts show an example of the operation of the image sensing apparatus in the one-shot AF mode.

Referring to FIG. 2, upon power ON after battery exchange or the like, the system control circuit 50 initializes flags, control variables, and the like and also performs required predetermined initial setups in the respective units of the image sensing apparatus 100 (S101).

The system control circuit 50 resets a dark end flag stored in its internal memory or the memory 52 (S102).

The system control circuit 50 checks the setup position of the power switch 72 (S103). If the power switch 72 is set at the power-OFF position, the system control circuit 50 executes a predetermined end process (S104). More specifically, the system control circuit 50 changes the indications of the respective indication units to an end state, records required parameters and setup values including flags, control variables, and the like, and the currently selected mode in the nonvolatile memory 56, cuts off unnecessary power supply to the respective units of the image sensing apparatus 100 including the image display unit 28 by the power supply control circuit 80, and so forth. After that, the flow returns to step S102.

If the power switch 72 is set at the power-ON position (S103), the power supply control circuit 80 detects the remaining capacity and operation state of the power supply 86 comprising batteries and the like, and the system control circuit 50 checks based on that detection result if these capacity and operation state pose any problem in the operation of the image sensing apparatus 100 (S105). If any problem is found, a predetermined alert indication is made by means of an image or voice using the indication unit 54 (S106), and the flow then returns to step S102.

If no problem is found in the power supply 86 (S105), the system control circuit 50 checks the setup position of the mode dial switch 60 (S107). If the mode dial switch 60 is set at one of the image sensing mode positions, the flow advances to step S109.

If the mode dial switch 60 is set at any of other mode positions (S107), the system control circuit 50 executes a process corresponding to the selected mode (S108), and the flow returns to step S102 upon completion of the process.

The system control circuit 50 checks if the recording medium 200 or 210 is attached, acquires management information of image data recorded on the recording medium 200 or 210, and then checks if the operation state of the recording medium 200 or 210 poses any problem in the operation of the image sensing apparatus 100, in particular, recording/playback of image data to/from the recording medium 200 or 210 (S109). If any problem is found, a predetermined alert indication is made by means of an image or voice using the indication unit 54 (S106), and the flow then returns to step S102.

If no problem is found, the flow advances to step S110, and the system control circuit 50 checks the setup state of the single/continuous shot switch 68 that sets the single/continuous shot mode (S110). If the single shot mode is selected, the circuit 50 sets a single/continuous shot flag to indicate the single shot mode (S111); if the continuous shot mode is selected, the circuit 50 sets the single/continuous shot flag to indicate the continuous shot mode (S112). Upon completion of flag setups, the flow advances to step S113.

With the single/continuous shot switch 68, the one-shot mode for sensing one frame of image upon depression of the shutter switch SW2, and then setting a standby state, and the continuous shot mode for successively sensing images while the shutter switch SW2 is held down can be arbitrarily selectively set.

Note that the state of the single/continuous shot flag is stored in the internal memory of the system control circuit 50 or the memory 52.

The system control circuit 50 indicates various setup states of the image display apparatus 100 by means of an image or voice using the indication unit 54 (S113). When the image display of the image display unit 28 is ON, various setup states of the image display apparatus 100 are indicated by means of an image also using the image display unit 28.

Referring to FIG. 3, if the shutter switch SW1 is OFF (S131), the flow returns to step S102.

If the shutter switch SW1 is ON (S131), the system control circuit 50 executes a distance measurement/photometry process (S132). More specifically, the system control circuit 50 executes a distance measurement process for bringing the photographing lens 310 into focus on an object, also executes a photometry process to determine the aperture value and shutter speed, and stores photometry data and/or setup parameters in its internal memory or the memory 52. In the photometry process, the electronic flash is set if necessary. The distance measurement/photometry process (S132) will be described in detail later with reference to FIG. 5.

The aperture value (Av value) and shutter speed (TV value) are determined on the basis of the stored photometry data and/or setup parameters, and the image sensing mode selected by the mode dial switch 60, the charge accumulation time is determined in accordance with the determined shutter speed (Tv value), and these determined values are stored in the internal memory of the system control circuit 50 or the memory 52 (S133). After that, the flow advances to step S134.

The system control circuit 50 checks the state of the single/continuous shot flag stored in its internal memory or the memory 52 (S134). If the single shot mode is set, the flow jumps to step S139.

In this manner, if it is determined in step S134 that the single shot mode is selected, the flow jumps to step S139 without executing a dark capture (1) process (S137; to be described later). With this control, a release time lag upon depression of the shutter switch SW2 in step S139 can be reduced, as will be described later.

If the continuous shot mode is selected (S134), the system control circuit 50 checks if the shutter switch SW2 is ON (S135). If the shutter switch SW2 is ON, the circuit 50 sets a dark end flag (S136), and the flow then jumps to step S161.

In this manner, if it is determined in step S134 that the continuous shot mode is selected, and the shutter switch SW2 is ON, the dark end flag is set, and the flow jumps to step S161 without executing dark capture (1) process (S137; to be described later). With this control, a release time lag upon depression of the shutter switch SW2 can be reduced by giving priority to an image sensing timing (to be described later) over the dark capture process.

In this case, as will be described later, the next frame of image is sensed in step S163, and a dark capture (2) process is done in step S166.

If the continuous shot mode is selected (S134), and if the shutter switch SW2 is OFF (S135), the system control circuit 50 executes a dark capture (1) process (S137). That is, the system control circuit 50 accumulates noise components such as dark current and the like of the image sensing element 14 for the same period of time as that required for actual image sensing, while closing the shutter 12, and reads out the accumulated noise image signal. After that, the flow advances to step S138.

By making correction computations using dark image data captured by the dark capture (1) process, sensed image data can be corrected in terms of image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element 14 and scratches unique to the image sensing element 14. The dark capture (1) process (S137) will be described in detail later using FIG. 7.

In this manner, if it is determined in step S134 that the continuous shot mode is set, but if continuous shot image sensing is not started as the shutter switch SW2 has not been pressed yet, the dark capture (1) process (S137) is executed prior to execution of the continuous shot image sensing, and hence nearly constant continuous-shot frame intervals can be set when continuous shot image sensing is done upon depression of the shutter switch SW2 in step S139, as will be described later.

The system control circuit 50 checks the state of the dark end flag stored in its internal memory or the memory 52 (S138), and if the dark end flag is set, the flow jumps to step S161.

In this manner, if the dark end flag is set in the dark capture (1) process routine (S137), the flow jumps to step S161, and a release time lag upon depression of the shutter switch SW2 can be reduced by giving priority to an image sensing timing over the dark capture process, as will be described later.

In this case, as will be described later, the next frame of image is sensed in step S163, and a dark capture (2) process is then executed in step S166.

If the dark end flag is reset (S138), the flow advances to step S139.

In such case, since the dark capture (1) process (S137) has been executed prior to continuous shot image sensing, nearly constant continuous-shot frame intervals can be set when continuous shot image sensing is done upon depression of the shutter switch SW2 in step S139, as will be described later.

If the shutter switch SW2 is OFF (S139), the system control circuit 50 checks if the shutter switch SW1 is ON (S140). If the shutter switch SW1 is ON, the flow returns to step S139.

If the shutter switch SW1 is turned off (S140), the flow returns to step S102.

If the shutter switch SW1 is turned on (S139), the flow advances to step S161.

Referring to FIG. 4, the system control circuit 50 checks if an area that can store sensed image data is available on an image storage buffer area on the memory 30 (S161). If no area that can store sensed image data is available on the image storage buffer area on the memory 30, a predetermined alert indication is made by means of an image or voice using the indication unit 54 (S162), and the flow then returns to step S102.

For example, the user experiences such state immediately after he or she has executed continuous shot image sensing corresponding to a maximum number of images that can be stored in the image storage buffer area. In this state, the first image to be read out from the memory 30 and written in the recording medium 200 or 210 is not recorded on the recording medium 200 or 210 yet, and a free area even for one image cannot be assured on the image storage buffer area on the memory 30.

When sensed image data is stored in the image storage buffer area on the memory 30 after it is compressed, it is checked in step S161 if an area that can store sensed image data is available on the image storage buffer area on the memory 30, in consideration of the fact that the compressed image data size varies depending on the setups of the compression mode.

If an area that can store sensed image data is available on the image storage buffer area on the memory 30 (S161), the system control circuit 50 executes an image sensing process (S163). More specifically, the system control circuit 50 reads out a sensed image signal, which has been accumulated for a predetermined period of time upon image sensing, from the image sensing element 14, and writes the sensed image data on the predetermined area of the memory 30 via the A/D converter 16, image processing circuit 20, and memory control circuit 22, or from the A/D converter 16 directly via the memory control circuit 22.

The image sensing process (S163) will be explained in detail later using FIG. 6.

Upon completion of the image sensing process (S163), the system control circuit 50 checks the state of the single/continuous shot flag stored in its internal memory or the memory 52 (S164).

As a result of checking the state of the single/continuous shot flag, if the single shot mode is selected (S164), the flow advances to step S166, and the system control circuit 50 executes a dark capture (2) process.

In this manner, if it is determined in step S164 that the single shot mode is selected, the system control circuit 50 executes the dark capture (2) process (S166) after the image sensing process (S163). With this control, a release time lag upon depression of the shutter switch SW2 in step S139 can be reduced.

On the other hand, as a result of checking the state of the single/continuous shot flag, if the continuous shot mode is selected (S164), the system control circuit 50 checks the state of the dark end flag stored in its internal memory or the memory 52 (S165). If the dark end flag is set, the flow advances to step S166.

In this manner, in continuous shot image sensing, when the dark capture (1) process (S137) is skipped to give priority to the image sensing timing and to reduce any release time lag upon depression of the shutter switch SW2, the dark capture (2) process is done in step S166 after the image sensing process (S163), as will be described later. If the dark end flag is reset (S165), the flow advances to step S167.

In this manner, in the continuous shot mode, when the dark capture (1) process has already been done in step S137, another dark capture (2) process (S166) is skipped.

The system control circuit 50 executes the dark capture (2) process for accumulating noise components such as dark current and the like of the image sensing element 14 for the same period of time as that required for actual image sensing, while closing the shutter 12, and reading out the accumulated noise image signal (S166). The flow then advances to step S167.

By making correction computations using-dark image data captured by the dark capture (2) process, sensed image data can be corrected in terms of image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element 14 and scratches unique to the image sensing element 14.

The dark capture (2) process (S166) will be described in detail later using FIG. 8.

Upon completion of the dark capture (2) process, the system control circuit 50 reads out some of image data written in the predetermined area of the memory 30 via the memory control circuit 22, executes a WB (white balance) integral computation process and OB (optical black) integral computation process required to execute development processes, and stores the computation results in its internal memory or the memory 52.

The system control circuit 50 reads out sensed image data written in the predetermined area of the memory 30 using the memory control circuit 22 and the image processing circuit 20 as needed, and executes various development processes including AWB (auto white balance) process, gamma conversion, color conversion, and the like using the computation results stored in its internal memory or the memory 52 (S167).

Furthermore, in the development processes, the system control circuit 50 also executes a dark correction computation process for canceling dark current noise and the like of the image sensing element 14 by executing a subtraction process using the dark image data captured in the dark capture process.

The system control circuit 50 reads out image data written in the predetermined area of the memory 30, makes the compression/expansion circuit 32 execute an image compression process in accordance with the selected mode (S168), and writes the image data that has sensed and undergone a series of processes in a free image space of the image storage buffer area on the memory 30.

Upon executing a series of processes, the system control circuit 50 starts a recording process for reading out image data stored in the image storage buffer area of the memory 30, and writing the readout image data in the recording medium 200 or 210 such as a memory card, compact flash card, or the like (S169).

This recording process is started for new image data, which has been sensed and undergone a series of processes, every time that image data is written in a free image space of the image storage buffer area on the memory 30.

While a write of image data in the recording medium 200 or 210 is underway, a recording medium write access indication (e.g., flashing an LED of the indication unit 54) is made to clearly indicate that write access.

The system control circuit 50 checks if the shutter switch SW1 is ON (S170).

If the shutter switch SW1 is OFF (S170), the flow returns to step S102.

If the shutter switch SW1 is ON (S170), the system control circuit 50 checks the state of the single/continuous shot flag stored in its internal memory or the memory 52 (S171), and if the single shot mode is selected, the flow returns to step S170 to repeat the current process until the shutter switch SW1 is turned off.

If the continuous shot mode is selected (S171), the flow returns to step S139 to proceed with image sensing, thus repeating a series of processes.

FIG. 5 is a flow chart showing the detailed sequence of the distance measurement/photometry process in step S132 in FIG. 3.

In the distance measurement/photometry process, the system control circuit 50 and the stop control circuit 340 or distance measurement control circuit 342 exchange various signals via the interface 120, connectors 122 and 322, interface 320, and lens control circuit 350.

The system control circuit 50 starts an AF (auto-focusing) process using the image sensing element 14, distance measurement circuit 42, and distance measurement control circuit 342 (S201).

The system control circuit 50 executes AF control for checking the focusing state of an image formed as an optical image by guiding light rays, which have entered the lens 310, to the distance measurement circuit 42 via the stop 312, lens mounts 306 and 106, mirror 130, and distance measurement sub-mirror (not shown), and detecting the focusing state using the distance measurement circuit 42 while driving the lens 310 using the distance measurement control circuit 342 (S202), until the distance measurement (AF) result indicates an in-focus (S203).

If the distance measurement (AF) result indicates an in-focus (S203), the system control circuit 50 determines an in-focus distance measurement point from those in an image sensing screen (S204), and stores distance measurement data and/or setup parameters in its internal memory or the memory 52 together with the determined distance measurement point data. The flow then advances to step S205.

Subsequently, the system control circuit 50 starts an AE (auto-exposure) process using the photometry circuit 46 (S205).

The system control circuit 50 executes a photometry process using the shutter control circuit 40 (S206) for measuring the exposure state of an image formed as an optical image by guiding light rays, which have entered the lens 310, to the photometry circuit 46 via the stop 312, lens mounts 306 and 106, mirrors 130 and 132, and photometry lens (not shown), until it is determined that the exposure (AE) value is appropriate (S207).

If it is determined that the exposure (AE) value is appropriate (S207), the system control circuit 50 stores photometry data and/or setup parameters in its internal memory or the memory 52, and the flow advances to step S208.

Note that the system control circuit 50 determines the aperture value (Av value) and shutter speed (Tv value) in accordance with the exposure (AE) result detected by the photometry process (S206) and the image sensing mode selected by the mode dial switch 60.

The system control circuit 50 determines the charge accumulation time of the image sensing element 14 in accordance with the determined shutter speed (Tv value), and executes the image sensing process and dark capture process using an equal charge accumulation time.

The system control circuit 50 checks based on the measurement data obtained by the photometry process (S206) if flash emission is required (S208). If flash emission is required, the circuit 50 sets a flash flag, and charges the electronic flash 48 (S209) until charging of the electronic flash 48 is completed (S210).

Upon completion of charging of the electronic flash 48 (S210), the distance measurement/photometry process routine (S132) ends.

FIG. 6 is a flow chart showing the detailed sequence of the image sensing process in step S163 in FIG. 4. In this image sensing process, the system control circuit 50 and the stop control circuit 340 or distance measurement control circuit 342 exchange various signals via the interface 120, connectors 122 and 322, interface 320, and lens system control circuit 350.

The system control circuit 50 moves the mirror 130 to a mirror up position using a mirror driving circuit (not shown) (S301), and drives the stop 312 to a predetermined aperture value by the stop control circuit 340 in accordance with photometry data stored in its internal memory or the memory 52 (S302).

The system control circuit 50 clears charge on the image sensing element 14 (S303), then starts charge accumulation of the image sensing element 14 (S304), opens the shutter 12 by the shutter control circuit 40 (S305), and starts exposure of the image sensing element 14 (S306).

The system control circuit 50 checks based on the flash flag if the electronic flash 48 is required (S307), and if the electronic flash 48 is required, the circuit 50 controls the electronic flash 48 to emit light (S308).

The system control circuit 50 waits for the end of exposure of the image sensing element 14 in accordance with the photometry data (S309), closes the shutter 12 by the shutter control circuit 40 (S310), and ends exposure of the image sensing element 14.

The system control circuit 50 drives the stop 312 to a full-open aperture value by the stop control circuit 340 (S311), and moves the mirror 130 to a mirror down position by the mirror driving circuit (not shown) (312).

If the determined charge accumulation time has elapsed (S313), the system control circuit 50 reads out a charge signal from the image sensing element 14 upon completion of charge accumulation of the image sensing element 14 (S314), and writes sensed image data in a predetermined area of the memory 30 via the A/D converter 16, image processing circuit 20, and memory control circuit 22, or from the A/D converter 16 directly via the memory control circuit 22 (S315).

Upon completion of a series of processes, the image sensing process routine (S163) ends.

FIG. 7 is a flow chart showing the detailed sequence of the dark capture (1) process in step S137 in FIG. 3.

The system control circuit 50 clears charge on the image sensing element 14 (S401).

If the shutter switch SW2 is turned on (S403) before the charge clear operation of the image sensing element 14 comes to an end (S402), the flow jumps to step S412. If the shutter switch SW2 is OFF (S403), the flow returns to step S401 to proceed with the charge clear operation of the image sensing element 14.

Upon completion of the charge clear operation of the image sensing element 14 (S402), the system control circuit 50 starts charge accumulation of the image sensing element 14 while the shutter 12 is closed (S404).

If the shutter switch SW2 is turned on (S406) before a predetermined charge accumulation time elapses (S405), the flow jumps to step S412. If the shutter switch SW2 remains OFF (S406), the flow returns to step S405.

If the predetermined charge accumulation time has elapsed (S405), the system control circuit 50 executes a dark image read process (S407). More specifically, the system control circuit 50 reads out a charge signal from the image sensing element 14 upon completion of charge accumulation of the image sensing element 14 (S407), and writes image data (dark image data) in a predetermined area of the memory 30 via the A/D converter 16, image processing circuit 20, and memory control circuit 22, or from the A/D converter 16 directly via the memory control circuit 22.

If the shutter switch SW2 stays OFF (S410) until a read of the dark image is completed (S409), the flow returns to step S408 to proceed with the dark image read process.

By executing the development process using this dark capture data, sensed image data can be corrected for image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element 14 and scratches unique to the image sensing element 14.

Note that this dark image data is held on the predetermined area of the memory 30 until a new distance measurement/photometry process is done or the power switch of the image sensing apparatus 100 is turned off. This dark image data is used when the next image sensing process is done, and image data sensed by that process is read out to execute the development process. Or when image data sensed by the image sensing process and read out from the image sensing element 14 has already been written in the memory 30, the development process is executed using dark image data.

If the shutter switch SW2 is turned on (S410) before a read of dark image data is completed (S409), the flow advances to step S412.

Upon completion of a read of dark image data (S409), the system control circuit 50 resets the dark end flag (S411), and then ends the dark capture (1) process routine (S137).

Or the system control circuit 50 sets the dark end flag (S412), and then ends the dark capture (1) process routine (S137).

In this manner, if the shutter switch SW2 is turned on during the dark capture (1) process, the dark end flag is set to forcibly end the dark capture process, thus giving priority to image sensing timing, and reducing any release time lag upon depression of the shutter switch SW2.

FIG. 8 is a flow chart showing the detailed sequence of the dark capture (2) process in step S166 in FIG. 4.

The system control circuit 50 clears charge on the image sensing element 14 (S501). Upon completion of the charge clear operation of the image sensing element 14 (S502), the system control circuit 50 starts charge accumulation of the image sensing element 14 while the shutter 12 is closed (S503).

If a predetermined charge accumulation time has elapsed (S504), the system control circuit 50 executes a dark image read process (S506). More specifically, the system control circuit 50 reads out a charge signal from the image sensing element 14 upon completion of charge accumulation of the image sensing element 14 (S505), and writes image data (dark image data) in a predetermined area of the memory 30 via the A/D converter 16, image processing circuit 20, and memory control circuit 22, or from the A/D converter 16 directly via the memory control circuit 22.

The flow returns to step S506 to proceed with the dark image read process until a read of dark image data is completed (S507).

By executing the development process using this dark capture data, sensed image data can be corrected for image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element 14 and scratches unique to the image sensing element 14.

Note that this dark image data is held on the predetermined area of the memory 30 until a new distance measurement/photometry process is done or the power switch of the image sensing apparatus 100 is turned off. This dark image data is used when the image sensing process is done later, and image data sensed by that process is read out to execute the development process. Or when image data sensed by the image sensing process and read out from the image sensing element 14 has already been written in the memory 30, the development process is executed using dark image data.

Upon completion of a read of dark image data (S507), the dark capture (2) process routine (S166) ends.

FIG. 9 is a timing chart showing the flow of image sensing operation in the first embodiment.

As can be seen from FIG. 9, in the continuous shot mode, the dark capture process is executed after the shutter switch SW1 is turned on. If the shutter switch SW2 stays OFF during execution of this dark capture process, the dark capture process comes to an end. As a result, even when continuous shot image sensing is done by turning on the shutter switch SW2 after that process, since the dark capture process is complete, nearly constant continuous shot frame intervals can be set.

On the other hand, in the continuous shot mode, the dark capture process is executed after the shutter switch SW1 is turned on. If the shutter switch SW2 is turned on before completion of the dark capture process, the dark capture process is forcibly ended, and image sensing is started. In this manner, priority is given to image sensing timing, and any release time lag upon depression of the shutter switch SW2 can be reduced. In this case, the dark capture process must be done after the first image sensing, and constant continuous shot frame intervals cannot always be set.

In case of the single shot mode, the dark capture process is done after image sensing, thus reducing any release time lag upon depression of the shutter switch SW2.

Second Embodiment

The second embodiment will be described below.

Since the arrangement of the second embodiment is basically the same as that of the first embodiment, the arrangement of the first embodiment will be used in the description of the second embodiment.

In the second embodiment, the contents of the control processes done by the image sensing apparatus are different from those of the first embodiment.

FIGS. 10 to 12 are flow charts of the main routine showing the control sequence of the image sensing apparatus according to the second embodiment. Note that the operation example of the image sensing apparatus in the one-shot AF mode has been explained in the first embodiment, but an operation example of the image sensing apparatus in a servo AF mode will be explained in the second embodiment.

Referring to FIG. 10, upon power ON after battery exchange or the like, the system control circuit 50 initializes flags, control variables, and the like and also performs required predetermined initial setups in the respective units of the image sensing apparatus 100 (S601).

The system control circuit 50 resets a dark end flag stored in its internal memory or the memory 52 (S602).

The system control circuit 50 checks the setup position of the power switch 72 (S603). If the power switch 72 is set at the power-OFF position, the system control circuit 50 executes a predetermined end process (S604). More specifically, the system control circuit 50 changes the indications of the respective indication units to an end state, records required parameters and setup values including flags, control variables, and the like, and the currently selected mode in the nonvolatile memory 56, cuts off unnecessary power supply to the respective units of the image sensing apparatus 100 including the image display unit 28 by the power supply control circuit 80, and so forth. After that, the flow returns to step S602.

If the power switch 72 is set at the power-ON position (S603), the power supply control circuit 80 detects the remaining capacity and operation state of the power supply 86 comprising batteries and the like, and the system control circuit 50 checks based on that detection result if these capacity and operation state pose any problem in the operation of the image sensing apparatus 100 (S605). If any problem is found, a predetermined alert indication is made by means of an image or voice using the indication unit 54 (S606), and the flow then returns to step S602.

If no problem is found in the power supply 86 (S605), the system control circuit 50 checks the setup position of the mode dial switch 60 (S607). If the mode dial switch 60 is set at one of the image sensing mode positions, the flow advances to step S609.

If the mode dial switch 60 is set at any of other mode positions (S607), the system control circuit 50 executes a process corresponding to the selected mode (S608), and the flow returns to step S602 upon completion of the process.

The system control circuit 50 checks if the recording medium 200 or 210 is attached, acquires management information of image data recorded on the recording medium 200 or 210, and then checks if the operation state of the recording medium 200 or 210 poses any problem in the operation of the image sensing apparatus 100, in particular, recording/playback of image data to/from the recording medium 200 or 210 (S609). If any problem is found, a predetermined alert indication is made by means of an image or voice using the indication unit 54 (S606), and the flow then returns to step S602.

If no problem is found, the flow advances to step S610, and the system control circuit 50 checks the setup state of the single/continuous shot switch 68 that sets the single/continuous shot mode (S610). If the single shot mode is selected, the circuit 50 sets a single/continuous shot flag to indicate the single shot mode (S611); if the continuous shot mode is selected, the circuit 50 sets the single/continuous shot flag to indicate the continuous shot mode (S612). Upon completion of flag setups, the flow advances to step S613.

With the single/continuous shot switch 68, the one-shot mode for sensing one frame of image upon depression of the shutter switch SW2, and then setting a standby state, and the continuous shot mode for successively sensing images while the shutter switch SW2 is held down can be arbitrarily selectively set.

Note that the state of the single/continuous shot flag is stored in the internal memory of the system control circuit 50 or the memory 52.

The system control circuit 50 indicates various setup states of the image display apparatus 100 by means of an image or voice using the indication unit 54 (S613). When the image display of the image display unit 28 is ON, various setup states of the image display apparatus 100 are indicated by means of an image also using the image display unit 28.

If the shutter switch SW1 is OFF in step S631 in FIG. 11, the flow returns to step S602.

If the shutter switch SW1 is ON (S631), the system control circuit 50 executes a distance measurement/photometry process (S632). More specifically, the system control circuit 50 executes a distance measurement process for bringing the photographing lens 310 into focus on an object, also executes a photometry process to determine the aperture value and shutter speed, and stores photometry data and/or setup parameters in its internal memory or the memory 52 (S632). In the photometry process, the electronic flash is set if necessary.

Since the detailed contents of the distance measurement/photometry process (S632) are the same as those in the first embodiment shown in FIG. 5, a detailed description thereof will be omitted.

The aperture value (Av value) and shutter speed (TV value) are determined on the basis of the stored photometry data and/or setup parameters, and the image sensing mode selected by the mode dial switch 60, the charge accumulation time is determined in accordance with the determined shutter speed (Tv value), and these determined values are stored in the internal memory of the system control circuit 50 or the memory 52 (S633). After that, the flow advances to step S634.

The system control circuit 50 checks the state of the single/continuous shot flag stored in its internal memory or the memory 52 (S634). If the single shot mode is set, the flow jumps to step S639.

In this manner, if it is determined in step S634 that the single shot mode is selected, the flow jumps to step S639 without executing a dark capture (1) process (S637). With this control, the release time lag upon depression of the shutter switch SW2 in step S639 can be reduced, as will be described later.

If the continuous shot mode is selected (S634), the system control circuit 50 checks if the shutter switch SW2 is ON (S635). If the shutter switch SW2 is ON, the circuit 50 sets a dark end flag (S636), and the flow then jumps to step S661.

In this manner, if it is determined in step S634 that the continuous shot mode is selected, and the shutter switch SW2 is ON, the dark end flag is set, and the flow jumps to step S661 without executing dark capture (1) process (S637). With this control, any release time lag upon depression of the shutter switch SW2 can be reduced by giving priority to image sensing timing (to be described later) over the dark capture process.

In this case, as will be described later, the next frame of image is sensed in step S663, and a dark capture (2) process is done in step S666.

If the continuous shot mode is selected (S634), and if the shutter switch SW2 is OFF (S635), the system control circuit 50 executes a dark capture (1) process (S637). That is, the system control circuit 50 accumulates noise components such as dark current and the like of the image sensing element 14 for the same period of time as that required for actual image sensing, while closing the shutter 12, and reads out the accumulated noise image signal. After that, the flow advances to step S638.

By making correction computations using dark image data captured by the dark capture (1) process, sensed image data can be corrected for image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element 14 and scratches unique to the image sensing element 14.

Since the detailed contents of this dark capture (1) process (S637) are the same as those in the first embodiment shown in FIG. 7, a detailed description thereof will be omitted.

In this manner, if it is determined in step S634 that the continuous shot mode is set, but if continuous shot image sensing is not started as the shutter switch SW2 has not been pressed yet, the dark capture (1) process (S637) is executed prior to continuous shot image sensing, and hence nearly constant continuous-shot frame intervals can be set when continuous shot image sensing is done upon depression of the shutter switch SW2 in step S639, as will be described later.

The system control circuit 50 checks the state of the dark end flag stored in its internal memory or the memory 52 (S638), and if the dark end flag is set, the flow jumps to step S661.

In this manner, if the dark end flag is set in the dark capture (1) process routine (S637), the flow jumps to step S661, and any release time lag upon depression of the shutter switch SW2 can be reduced by giving priority to image sensing timing over the dark capture process, as will be described later.

In this case, as will be described later, the next frame of image is sensed in step S663, and a dark capture (2) process is then executed in step S666.

If the dark end flag is reset (S638), the flow advances to step S639.

In such case, since the dark capture (1) process (S637) has been executed prior to continuous shot image sensing, nearly constant continuous-shot frame intervals can be set when continuous shot image sensing is done upon depression of the shutter switch SW2 in step S639, as will be described later.

If the shutter switch SW2 is OFF (S639), the system control circuit 50 checks if the shutter switch SW1 is ON (S640). If the shutter switch SW1 is ON, the flow returns to step S632 to repeat a series of processes.

If the shutter switch SW1 is turned off (S640), the flow returns to step S602. If the shutter switch SW1 is turned on (S639), the flow advances to step S661.

Referring to FIG. 12, the system control circuit 50 checks if an area that can store sensed image data is available on an image storage buffer area on the memory 30 (S661). If no area that can store sensed image data is available on the image storage buffer area on the memory 30, a predetermined alert indication is made by means of an image or voice using the indication unit 54 (S662), and the flow then returns to step S602.

For example, the user experiences such state immediately after he or she has executed continuous shot image sensing corresponding to a maximum number of images that can be stored in the image storage buffer area. In this state, the first image to be read out from the memory 30 and written in the recording medium 200 or 210 is not recorded on the recording medium 200 or 210 yet, and a free area even for one image cannot be assured on the image storage buffer area on the memory 30.

When sensed image data is stored in the image storage buffer area on the memory 30 after it is compressed, it is checked in step S661 if an area that can store sensed image data is available on the image storage buffer area on the memory 30, in consideration of the fact that the compressed image data size varies depending on the setups of the compression mode.

If an area that can store sensed image data is available on the image storage buffer area on the memory 30 (S661), the system control circuit 50 executes an image sensing process (S663). More specifically, the system control circuit 50 reads out a sensed image signal, which has been accumulated for a predetermined period of time upon image sensing, from the image sensing element 14, and writes the sensed image data on the predetermined area of the memory 30 via the A/D converter 16, image processing circuit 20, and memory control circuit 22, or from the A/D converter 16 directly via the memory control circuit 22.

Since the detailed contents of the image sensing process (S663) are the same as those in the first embodiment shown in FIG. 6, a detailed description thereof will be omitted.

Upon completion of the image sensing process (S663), the system control circuit 50 checks the state of the single/continuous shot flag stored in its internal memory or the memory 52 (S664).

As a result of checking the state of the single/continuous shot flag, if the single shot mode is selected (S664), the flow advances to step S666, and the system control circuit 50 executes a dark capture (2) process.

In this manner, if it is determined in step S664 that the single shot mode is selected, the system control circuit 50 executes the dark capture (2) process (S666) to be described later after the image sensing process (S663). With this control, the release time lag upon depression of the shutter switch SW2 in step S639 can be reduced.

On the other hand, as a result of checking the state of the single/continuous shot flag, if the continuous shot mode is selected (S664), the system control circuit 50 checks the state of the dark end flag stored in its internal memory or the memory 52 (S665). If the dark end flag is set, the flow advances to step S666.

In this manner, in continuous shot image sensing, when the dark capture (1) process (S637) is skipped to give priority to image sensing timing and to reduce the release time lag upon depression of the shutter switch SW2, the dark capture (2) process is done in step S666 after the image sensing process (S663), as will be described later. If the dark end flag is reset (S665), the flow advances to step S667.

In this manner, in the continuous shot mode, when the dark capture (1) process has already been done in step S637, another dark capture (2) process (S666) is skipped.

The system control circuit 50 executes the dark capture (2) process for accumulating noise components such as dark current and the like of the image sensing element 14 for the same period of time as that required for actual image sensing, while closing the shutter 12, and reading out the accumulated noise image signal (S666). The flow then advances to step S667.

By making correction computations using dark image data captured by the dark capture (2) process, sensed image data can be corrected for image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element 14 and scratches unique to the image sensing element 14.

Since the detailed contents of this dark capture (2) process (S666) are the same as those in the first embodiment shown in FIG. 8, a detailed description thereof will be omitted.

Upon completion of the dark capture (2) process, the system control circuit 50 reads out some of image data written in the predetermined area of the memory 30 via the memory control circuit 22, executes a WB (white balance) integral computation process and OB (optical black) integral computation process required to execute development processes, and stores the computation results in its internal memory or the memory 52.

The system control circuit 50 reads out sensed image data written in the predetermined area of the memory 30 using the memory control circuit 22 and the image processing circuit 20 as needed, and executes various development processes including AWB (auto white balance) process, gamma conversion, color conversion, and the like using the computation results stored in its internal memory or the memory 52 (S667).

Furthermore, in the development processes, the system control circuit 50 also executes a dark correction computation process for canceling dark current noise and the like of the image sensing element 14 by executing a subtraction process using the dark image data captured in the dark capture process.

The system control circuit 50 reads out image data written in the predetermined area of the memory 30, makes the compression/expansion circuit 32 execute an image compression process in accordance with the selected mode (S668), and writes the image data that has sensed and undergone a series of processes in a free image space of the image storage buffer area on the memory 30.

Upon executing a series of processes, the system control circuit 50 starts a recording process for reading out image data stored in the image storage buffer area of the memory 30, and writing the readout image data in the recording medium 200 or 210 such as a memory card, compact flash card, or the like (S669).

This recording process is started for new image data, which has been sensed and undergone a series of processes, every time that image data is written in a free image space of the image storage buffer area on the memory 30.

While a write of image data in the recording medium 200 or 210 is underway, a recording medium write access indication (e.g., flashing an LED of the indication unit 54) is made to clearly indicate that write access.

The system control circuit 50 checks if the shutter switch SW1 is ON (S670).

If the shutter switch SW1 is OFF (S670), the flow returns to step S602.

If the shutter switch SW1 is ON (S670), the system control circuit 50 checks the state of the single/continuous shot flag stored in its internal memory or the memory 52 (S671), and if the single shot mode is selected, the flow returns to step S670 to repeat the current process until the shutter switch SW1 is turned off.

If the continuous shot mode is selected (S671), the flow returns to step S632 to proceed with image sensing, thus repeating a series of processes.

FIG. 13 is a timing chart showing the flow of image sensing operation in the second embodiment.

As can be seen from FIG. 13, in the second embodiment, after the shutter switch SW1 is turned on, the auto-focusing (AF) process, auto-exposure (AE) process, and dark capture (1) process are repeated in the continuous shot mode, or the auto-focusing (AF) process and auto-exposure (AE) process are repeated in the single shot mode until the shutter switch SW2 is turned on. In the first embodiment, the processes are not repeated in such way.

By repeating the processes, in the second embodiment, even when the time interval between the ON timings of the shutter switches SW1 and SW2 is long, and the focusing state, exposure data, and dark image data have changed over time, the image sensing process can be done based on the latest data.

In the first and second embodiments, the single or continuous shot mode is selected using the single/continuous shot switch 68. Alternatively, the single or continuous shot mode may be selected in correspondence with the operation mode selected by the mode dial switch 60.

In each of the above embodiments, the charge accumulation time of the actual image sensing process is set to be equal to that of the dark capture process. However, different charge accumulation times may be set as long as sufficient data that can be used to correct dark current noise and the like can be obtained.

During execution of the dark capture (2) process in step S166 or S666, since image sensing cannot be done, a visual or audio message indicating that the dark capture process of the image sensing apparatus 100 cannot be canceled may be made using the indication unit 54 and/or image display unit 28.

On the other hand, during execution of the dark capture (1) process in step S137 or S637, since the dark capture process can be canceled by pressing the shutter switch SW2 and actual image sensing can be done preferentially, a visual or audio message indicating that the dark capture process of the image sensing apparatus 100 can be canceled may be made using the indication unit 54 and/or image display unit 28. For example, if the dark capture process cannot be canceled, a red LED may be turned on; if the dark capture process can be canceled, a green LED may be turned on, so as to indicate different messages. Or if the dark capture process cannot be canceled, an LED may flicker quickly; if the dark capture process can be canceled, a green LED may flicker slowly, so as to indicate different messages.

Furthermore, the first embodiment has exemplified the operation in the one-shot AF mode, and the second embodiment has exemplified the operation in the servo AF mode. The operation may be switched by an AF mode (one-shot AF mode or servo AF mode) selected by an AF mode setup switch.

In the description of each embodiment, image sensing is done by moving the mirror 130 between the mirror up and down positions. However, the mirror 130 may comprise a half mirror, and image sensing may be done without moving the mirror.

Note that the recording media 200 and 210 are not limited to memory cards such as PCMCIA cards, compact flash cards, or the like, hard disks, and the like, but may use micro DATs (digital audio tapes), magneto-optical disks, optical disks such as CD-Rs, CD-WRs, or the like, phase change optical disks such as DVDs, and the like.

Also, the recording media 200 and 210 may use hybrid media that integrate memory cards, hard disks, and the like. Furthermore, such hybrid media may include detachable media.

In the description of the embodiment, the recording media 200 and 210 are independent from the image sensing apparatus 100 and are arbitrarily connectable. One or both the recording media 200 and 210 may be permanently connected to the image sensing apparatus 100.

An arbitrary number (one or a plurality) of image recording media 200 or 210 may be connectable to the image sensing apparatus 100.

In the above description, the recording media 200 and 210 are attached to the image sensing apparatus. However, one or a combination of a plurality of recording media may be used.

In each of the above embodiments, an explanation has been given using the CCD as an example of the image sensing element 14. Also, when the image sensing element uses a CMOS, the above effects can be obtained.

The embodiments of the present invention have been described. However, the present invention is not limited to the arrangements of such embodiments, but may be applied to any other arrangements as long as they may achieve functions defined in the appended claims or functions of the arrangements of the embodiments.

For example, in each of the above embodiments, the dark image capture process prior to image sensing is done in the continuous shot mode. However, the present invention is not limited to such specific mode. For example, the dark image capture process prior to image sensing may be done in a servo auto-focusing mode. Furthermore, the present invention can be applied to any other systems that can switch whether the dark image capture process is done before or after image sensing as needed.

The software and hardware arrangements of the above embodiments can be appropriately replaced.

The present invention may be achieved by combining the above embodiments or their technical components as needed.

The present invention may be applied even when all or some of claims or the arrangements of the embodiments form a single apparatus, are combined with another apparatus, or are building components of the apparatus.

The present invention can be applied to various types of cameras such as an electronic still camera, video movie camera, a camera using a silver halide film, and the like, image sensing apparatuses other than cameras, devices applied to such cameras and image sensing apparatuses, and building components of those devices.

Note that the present invention may be applied to either a system constituted by a plurality of devices, or an apparatus consisting of a single equipment.

The objects of the present invention are also achieved by supplying a storage medium, which records a program code of a software program that can implement the functions of the above-mentioned embodiments to the system or apparatus, and reading out and executing the program code stored in the storage medium by a computer (or a CPU or MPU) of the system or apparatus.

In this case, the program code itself read out from the storage medium implements the functions of the above-mentioned embodiments, and the storage medium which stores the program code constitutes the present invention.

As the storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magnetooptical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, and the like may be used.

The functions of the above-mentioned embodiments may be implemented not only by executing the readout program code by the computer but also by some or all of actual processing operations executed by an OS (operating system) running on the computer on the basis of an instruction of the program code.

Furthermore, the functions of the above-mentioned embodiments may be implemented by some or all of actual processing operations executed by a CPU or the like arranged in a function extension board or a function extension unit, which is inserted in or connected to the computer, after the program code read out from the storage medium is written in a memory of the extension board or unit. 

What is claimed is:
 1. An apparatus comprising: (A) an image sensing device; (B) a signal processing device for performing a first image sensing operation for causing said image sensing device to perform an image sensing operation in an exposure state, and a second image sensing operation for causing said image sensing device perform an image sensing operation in a non-exposure state, and processing a first image signal obtained by the first image sensing operation by a second image signal obtained by the second image sensing operation, said signal processing device having a first mode for causing said image sensing device perform the first image sensing operation and then the second image sensing operation, and a second mode for causing said image sensing device to perform the second image sensing operation and then the first image sensing operation; and (C) a storage device for storing signals obtained in the first and second modes processed by said signal processing device.
 2. The apparatus according to claim 1, wherein said storage device compresses a signal processed by said signal processing device, and stores the compressed signal.
 3. The apparatus according to claim 2, wherein said storage device includes a buffer.
 4. The apparatus according to claim 3, further comprising a recording device for recording information stored in said storage device in a recording medium.
 5. The apparatus according to claim 4, further comprising a switching device for switching said signal processing device between the first and second modes by external operation.
 6. The apparatus according to claim 5, wherein said switching device switches between single and continuous shot modes upon switching between the first and second modes.
 7. The apparatus according to claim 6, wherein said switching device switches to the single shot mode upon switching to the first mode, and switches to the continuous shot mode upon switching to the second mode.
 8. The apparatus according to claim 1, further comprising a switching device for switching said signal processing device between the first and second modes by external operation.
 9. The apparatus according to claim 8, wherein said switching device switches between single and continuous shot modes upon switching between the first and second modes.
 10. The apparatus according to claim 1, further comprising a switching device for switching said signal processing device between the first and second modes in accordance with an image sensing mode.
 11. The apparatus according to claim 1, further comprising a switching device for switching said signal processing device between the first and second modes in accordance with a state of shutter release operation.
 12. The apparatus according to claim 1, wherein said apparatus includes a camera.
 13. An apparatus comprising: (A) an image sensing device; (B) a signal processing device for performing a first image sensing operation for causing said image sensing device to perform an image sensing operation in an exposure state, and a second image sensing operation for causing said image sensing device to perform an image sensing operation in a non-exposure state, and processing a first image signal obtained by the first image sensing operation by a second image signal obtained by the second image sensing operation, said signal processing device having a first mode for causing said image sensing device to perform the first image sensing operation and then the second image sensing operation, and a second mode for causing said image sensing device to perform the second image sensing operation and then the first image sensing operation; and (C) a switching device for switching said signal processing device between the first and second modes in accordance with a state of shutter release operation.
 14. The apparatus according to claim 13, wherein said signal processing device operates in the first mode in a single shot mode, and operates in the second mode in a continuous shot mode.
 15. The apparatus according to claim 13, wherein said apparatus includes a camera.
 16. An apparatus comprising: (A) an image sensing device; (B) a signal processing device for performing a first image sensing operation for causing said image sensing device to perform an image sensing operation in an exposure state, and a second image sensing operation for causing said image sensing device to perform an image sensing operation in a non-exposure state, and processing a first image signal obtained by the first image sensing operation by a second image signal obtained by the second image sensing operation, said signal processing device having a first mode for causing said image sensing device to perform the first image sensing operation and then the second image sensing operation, and a second mode for causing said image sensing device to perform the second image sensing operation and then the first image sensing operation; (C) an exposure start instruction device for instructing start of exposure by external operation; and (D) a switching device for switching said signal processing device to the first mode when said exposure start instruction device issues an exposure start instruction while said signal processing device is executing the second image sensing operation in the second mode.
 17. The apparatus according to claim 16, wherein said signal processing device operates in the first mode in a single shot mode, and operates in the second mode in a continuous shot mode.
 18. The apparatus according to claim 16, wherein said apparatus includes a camera.
 19. An apparatus comprising: (A) an image sensing device; (B) an exposure instruction device for issuing an exposure preparation instruction at a first stroke position of a shutter release member, and issuing an exposure start instruction at a second stroke position of the shutter release member; and (C) a signal processing device for performing a first image sensing operation for causing said image sensing device to perform an image sensing operation in an exposure state, and a second image sensing operation for causing said image sensing device to perform an image sensing operation in a non-exposure state, and processing a first image signal obtained by the first image sensing operation by a second image signal obtained by the second image sensing operation, said signal processing device performing the second image sensing operation in response to the exposure preparation instruction issued by said exposure instruction device, and performing the first image sensing operation in response to the exposure start instruction issued by said exposure instruction device.
 20. The apparatus according to claim 19, wherein said apparatus includes a camera. 